angular route resolver or onInit?

Question

What better for using resolver service or get data in OnInit hook? For example, if I need get data from 3 different sources into 1 page better user resolver or write code into ngOnInit?

code

ngOnInit() {
  service1.getData().subscribe(c => {
    this.data1 = c;
  });
  service2.getData().subscribe(c => {
    this.data2 = c;
  });
  service3.getData().subscribe(c => {
    this.data3 = c;
  });
}

OR

RouterModule.forRoot([{
  path: 'page/:id',
  component: blabla,
  resolve: {
    data1: service1,
    data2: service2,
    data3: service3
  }
}])

ngOnInit() {
  this.data1 = this.activatedRoute.snapshot.data.data1;
  this.data2 = this.activatedRoute.snapshot.data.data2;
  this.data3 = this.activatedRoute.snapshot.data.data3;
}

Answer 1

The main difference between resolvers and onInit is the synchronicity.

• Resolver is synchronous.

  • You should use it when you need the data before the component is loaded.
  • You block the component loading.
  • You don't inject the service into the component (you can't use other methods there)

• OnInit is asynchronous (in your code).

  • You should use it when there is no need for the data being available before loading the component.
  • You don't block the component loading.
  • You inject the service into the component, therefore you can use other methods from this service.

Take a look at this site: https://blog.thoughtram.io/angular/2016/10/10/resolving-route-data-in-angular-2.html